<html>
<head>
<title>test</title>
<meta charset="UTF-8"/>
<script type="text/javascript">
var a=0;
var t;
function f () {
document.getElementById("di").value=a;
a++;
t=setTimeout("f()",1000);
}
function ff () {
document.getElementById("di").value=a;
clearTimeout(t);
}
function fff () {
document.getElementById("di").value=0;
clearTimeout(t);
a=0;
}
</script>
</head>
<body>
<button onclick="f()">click</button>
<input id="di" type="text" value=0>
<button onclick="ff()">stop</button>
<button onclick="fff()">again</button>
</body>
</html>
